南海北部珠江口—琼东南盆地地壳速度结构与几何分层
摘要
基于南海北部大陆边缘珠江口—琼东南盆地深水区实施的14条近垂直深反射地震探测叠加速度谱,利用Dix公式将叠加速度剖面转换为地壳层速度剖面,并利用时深转换方法构建了深度域地壳层速度模型,综合各地壳速度剖面分析了南海北部大陆边缘珠江口与琼东南盆地不同深度层次的P波速度变化趋势以及地壳几何分层特征.结果表明,琼东南盆地区可分为4-v8 km沉积层(V_p为1.7-4.7 km/s),4-10 km厚的E.地壳层(V_p为5.2-6.3 km/s)、5km左右的下地壳层(VP为6.4-7.0 km/s)以及2-6 km厚的高速下地壳底层(V_p>7.0 km/s).Vp>7.0 km/s下地壳高速层的存在被认为是岩石圈伸展、下地壳底部底辟构造或者是残存的原始华夏下地壳基性层的地震学指示;综合研究区地球物理探测成果构建了跨越华南大陆与南海北部陆坡区剖面莫霍和岩石圈底界图像,揭示出岩石圈上地幔在华南大陆与南海北部大陆边缘的减薄特征.
Base on stack velocity spectrum dataset of 14 near-vertical deep reflection profiles in the Zhujiang River estuary-Qiongdongnan basin in the continental margin of northern South China Sea, we use Dix formula to transform the corresponding stack velocities into the crustal-layervelocities (in TWT domain) and convert the layer velocities into the depth domain by time-depth transformation scheme. Integrating all the crustal velocity models, we analyze the spatial variation of P wave velocity in different depths and the stratified geometry of crust in the Yinggehai and Qiongdongnan basin area in the continent margin of northern South China Sea. The results demonstrate that the kinematic structure of Qiongdongnan basin can be divided into 4 -8km thick sediment layer (V_P is 1. 7-4. 7 km/s) , 4-10 km thick upper crust (V_P is 5. 2-6. 3 km/s), about 5 km thick normal lower crust (V_P is 6. 4-7. 0 km/s) and about 2-6 km thick anomalous lower crust with high velocity (>7. 0 km/s). The existence of anomalous lower crust layer with high velocities >7. 0 km/s can be considered as seismic signature of the underplating at the lower crust bottom induced by lithosphere extension in South China and its continental margin, or the residual mafic layer of the extended Cathaysia lower crust. Integrating the related geophysical sounding results, we construct the depth images of Moho and the lithosphere bottom across the continent of South China and the continental slope of South China Sea, which reveals the lithosphere thinning across continental South China and the continental margin of the South China sea.
Base on stack velocity spectrum dataset of 14 near-vertical deep reflection profiles in the Zhujiang River estuary-Qiongdongnan basin in the continental margin of northern South China Sea, we use Dix formula to transform the corresponding stack velocities into the crustal-layervelocities (in TWT domain) and convert the layer velocities into the depth domain by time-depth transformation scheme. Integrating all the crustal velocity models, we analyze the spatial variation of P wave velocity in different depths and the stratified geometry of crust in the Yinggehai and Qiongdongnan basin area in the continent margin of northern South China Sea. The results demonstrate that the kinematic structure of Qiongdongnan basin can be divided into 4 -8km thick sediment layer (V_P is 1. 7-4. 7 km/s) , 4-10 km thick upper crust (V_P is 5. 2-6. 3 km/s), about 5 km thick normal lower crust (V_P is 6. 4-7. 0 km/s) and about 2-6 km thick anomalous lower crust with high velocity (>7. 0 km/s). The existence of anomalous lower crust layer with high velocities >7. 0 km/s can be considered as seismic signature of the underplating at the lower crust bottom induced by lithosphere extension in South China and its continental margin, or the residual mafic layer of the extended Cathaysia lower crust. Integrating the related geophysical sounding results, we construct the depth images of Moho and the lithosphere bottom across the continent of South China and the continental slope of South China Sea, which reveals the lithosphere thinning across continental South China and the continental margin of the South China sea.
引文
[1] 刘光鼎.中国海区及邻域地质地球物理系列图.北京:地质出版社,1994 Liu G D. Geophysical Field Features of China Sea and Adjacent Regions. Beijing: Geological Publishing House, 1994
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[3] 龚再升,李思田等.南海北部大陆边缘盆地分析与油气聚集.北京:科学出版社,1997 Gong Z S, Li S T, et al. Continental Margin Basin Analysis and Hydrocarbon Accumulation of Northern South China Sea (in Chinese). Beijing: Science Press, 1997
[4] 郭令智,施央申,马荣生.西太平洋中新生代活动大陆边缘和岛弧构造的形成和演化.地质学报,1983,57(1) :11-12 Guo L Z, Shi Y S, Ma R S. On the formation and evolution of the mesozoic-cenozoic active continental margin and island arc tectonics of the western pacific ocean. Acta Geologica Sinica (in Chinese) , 1983,57(1) :11-12
[5] 林长松,虞夏军.南海海盆扩张成因质疑.海洋学报,2006,28(1) :67-76 Lin C S, Yu X J, Question on the spreading of the South China Sea Basin. Acta Oceanologica Sinica ( in Chinese), 2006,28(1) :67-76
[6] 刘昭蜀,赵焕庭,范时清等.南海陆缘地堑系及边缘海的演化旋回.见:南海地质.北京:科学出版社,2001 Liu Z S, Zhao H T ,Fan S Q, The continental margin spreading of South China Sea and the cycle of evolution of marginal seas. In:Journal of Tropical Oceanography ( in Chinese). Beijing: Science Press, 2001
[7] 张云帆,孙珍,周蒂等.南海北部陆缘新生代地壳减薄特征及其动力学意义.中国科学,2007,37(12) :1609-1616 Zhang Y F, Sun Z, Zhou D, et al. The Cenozoic crust thinning characteristics and its dynamics meaning of northern margin of South China Sea. Science in China (in Chinese).2007,37(12) :1609-1616
[8] 周蒂,刘海龄.南沙海区及其周缘中一新生代岩浆活动及构造意义.大地构造与成矿学,2005,29(3) :354-363 Zhou D, Liu H L. Mesozoic-Cenozoic magmatism in southern South China Sea and its surrounding areas and its implications to tectonics. Geotectonica et Metallogenia (in Chinese). 2005,29(3) :354-363
[9] 周蒂,陈汉宗.南海的右行陆缘裂解成因.地质学报,2002,76(2) :180-190 Zhou D,Chen H Z, Opening of the South China Sea by dextral splitting of the East Asian Continental margin. Acta Geologica Sinica (in Chinese), 2002,76(2) :180-190
[10] 何廉声.南海地质构造图.见:南海地质地球物理图集.广州:广东科技出版社,1987 He L S. Geological structure map of South China Sea. In:Geology and Geophysics Atlas of South China Sea (in Chinese). Guangzhou: Guangdong Science and Technology Press, 1987
[11] Tian Z, Han P, Xu K. The Mesozoic-Cenozoic East China rift system. Tectonophysics, 1992,208(1-3) :341-363
[12] 袁玉松.南海北部陆缘深水区构造-热演化与烃源岩成熟度史研究[博士学位论文].北京:中国科学院地质与地球物理研究所,2007 Yuan Y S. Tectonothermal evolution and source rock maturation history in deep water area of the northern margin of the South China Sea [Ph. D. thesis](in Chinese). Beijing: Institute of Geology and Geophysics, Chinese Academy of Sciences, 2007
[13] 张功成,米立军,吴时国等.深水区-南海北部大陆边缘盆地油气勘探新领域.石油学报,2007,28(2) :15-21 Zhang G C, Mi L J, Wu S G, et al. Deepwater area-the new prospecting targets of northern continental margin of South China Sea. Acta Petrolei Sinica (in Chinese), 2007,28 (2) :15-21
[14] Karig D E. Origin and development of marginal basins in the western Pacific. J. Geophys. Res. ,1971,76:2543-2561
[15] Tapponnier P, Molnar P. Slip-line field theory and large scale continental tectonics. Nature, 1976,264:319-324
[16] 阎贫,刘海龄.南海北部陆缘地壳结构探测结果分析.热 带海洋学报,2002,21(2) :1-12 Yan P, Liu H L. Analysis on deep crust sounding resulting northern margin of South China Sea. Tropic Oceanology (in Chinese), 2002,21(2) : 1-12
[17] 姚伯初,万玲,吴能友.南海新生代构造演化及岩石圈三维结构特征.地质通报,2005,24(1) :1-8 Yao B C. Wan L, Wu N Y. Cenozoic tectonic evolution and the 3D structure of the lithosphere of the South China Sea. Regional Geology of China (in Chinese), 2005,24(1) :1-8
[18] 王家林,张新兵,吴健生等.珠江口盆地基底结构的综合地球物理研究.热带海洋学报,2002,21(2) :14-22 Wang J L, Zhang X B, Wu J S et al. Integrated geophysical researches on base texture of Zhujiang River Mouth Basin. Tropic Oceanology (in Chinese), 2002 ,21(2) :14-22
[19] Nissen S, Hayes D, Buhl P, et al. Deep penetration seismic sounding across the north margin of South China Sea. J. Geophys. Res., 1995,100(Bl1) :22407-22433
[20] Nissen S, Hayes D, Yao B, et al. Gravity, heat flow, and seismic constraints on the processes of crustal extension: Northern margin of South China Sea. J. Geophys. Res. , 1995,100(1111) :22447-22483
[21] 滕吉文,王谦身,魏斯禹.中国地壳构造的基本轮廓.石油物探,1982,2:14-30 Teng J W, Wang Q S, Wei S Y. The basic contour map of China crustal structure. Geophysical Prospecting for Petroleum (in Chinese), 1982,2:14-30
[22] Christensen N I, Mooney W D. Seismic velocity structure and composition of the continental crust; a global view. J. Geophys. Res. ,1995,100:9761-9788
[23] Zhang Z J, Zhang X, Badal J. Composition of the crust beneath Southeastern China derived from an integrated geophysical dataset. Journal of Geophysical Research , 2008 , 113(B4) , B04417, doi:10． 1029/2006JB004503
[24] Zhang Z J, Badal J, Li Y, et al. Crust-upper mantle seismic velocity structure across Southeastern China. Tectonophysics , 2005, 395:137-157
[25] Zhang Z J. Wang Y H. Crustal structure and contact relationship revealed from deep seismic sounding data in South China. Physics of the Earth and Planetary Interiors , 2007,165:114-126
[26] 袁学诚,左愚,蔡学林等.华南板块岩石圈构造与地球物理.见:80年代中国地球物理学进展.北京:学术书刊出版社.1989． 243-249 Yuan X C, Zuo Y, Cai X L, et al. The structure of the lithosphere and the geophysics in the South China plate geophysics in China. In Commemoration of the 80th Birthday of Professor Fu Chengyi (in Chinese). Beijing: Academic Journal Press, 1989． 243-249
[27] 廖其林,王振明,朱介寿.福州-泉州-汕头地区地壳结构的爆炸地震研究.地球物理学报,1986,3:270-280 Liao Q L, Wang Z M, Zhu J S. Explosion seismic study of the crustal structure in Fuzhou-Quanzhou-Shantou region. Chinese J.Geophys. (in Chinese), 1986,3:270-280
[28] Fan W, Amenzies M. The lithospheric mantle composition of volcanism in extension settings: the geochemical evidence of Cenozoic basalts in Leiqiung area. lit; Liu R Ed. The Ages and Geochemistry of Cenozoic Volcanic Rocks in China. Beijing:Seismological Press,1992． 320-329
[29] Zhu B, Wang H. Nd-Sr-Pb isotope and chemical evidence for the volcanism with MORB-OIB source characteristics in the Leiqiong area, China. Geochimica, 1989,18(3) :193-201
[30] Xia B, Zhang Y, Cui X J, et al. Understanding of the geological and geodynamie controls on the formation of the South China Sea:A numerical modelling approach. Journal of Geodynamics,2006,42:63-84．
[31] Zhang Z J, Bai Z M, Mooney W D, et al. Crustal structure across the Three Georges areas of the Yangtze platform, central China, from seismic refraction/wide-angle reflection data. Tectonophysics, 2009,475:423-437, doi:10． 1016/j. tecto. 2009． 05． 022
[32] Thybo H, Maguire P K H, Birt C.et al. Seismic reflectivity and magmatic underplating beneath the Kenga Rift. Geophys. Res. Lett. , 2000,27( 17) :2745-2748
[33] Thybo H, Nielsen C A. Magma-compensated crustal thinning in continental rift zones. Nature,2009,457:873-876
[34] 张中杰,刘一峰,张素芳等.东南盆地地壳伸展特征及其动力学意义.地球物理学报,2009(待发表) Zhang Z J, Liu Y F. Zhang S F, et al. Crustal extension fatures in Qiongdannan basin and its tectonic implications. Submitted to Chinese J. Geophys. (in Chinese), 2009
[35] Wang Y J, Fan W M, Guo F, et al. Geochemistry of Mesozoic mafic rocks adjacent to the chenzhou-cinwufault, South China. Implication for the lithospheric boundary between the Yangtze and Cathaysia blocks. Int. Geol. Rev. ,2003,45:263-286
[36] Li Z X, Li X H. Formation of the 1300 km wide intracontinental-orogen and postorogenic magmatic province in Mesozoic South China; A flat-slab subduction model. Geology, 2007 ,35:179-182
[2] 陈国达.东亚陆缘扩张带-1条离散式大陆边缘成因的探讨.大地构造与成矿学,1997,21(4) :285-293 Chen G D. The marginal extensional belt of East Asia continental; investigating the origin of a discrete continental margin. Geotectonica et Metallogenia (in Chinese) , 1997,21 (4) :285-293
[3] 龚再升,李思田等.南海北部大陆边缘盆地分析与油气聚集.北京:科学出版社,1997 Gong Z S, Li S T, et al. Continental Margin Basin Analysis and Hydrocarbon Accumulation of Northern South China Sea (in Chinese). Beijing: Science Press, 1997
[4] 郭令智,施央申,马荣生.西太平洋中新生代活动大陆边缘和岛弧构造的形成和演化.地质学报,1983,57(1) :11-12 Guo L Z, Shi Y S, Ma R S. On the formation and evolution of the mesozoic-cenozoic active continental margin and island arc tectonics of the western pacific ocean. Acta Geologica Sinica (in Chinese) , 1983,57(1) :11-12
[5] 林长松,虞夏军.南海海盆扩张成因质疑.海洋学报,2006,28(1) :67-76 Lin C S, Yu X J, Question on the spreading of the South China Sea Basin. Acta Oceanologica Sinica ( in Chinese), 2006,28(1) :67-76
[6] 刘昭蜀,赵焕庭,范时清等.南海陆缘地堑系及边缘海的演化旋回.见:南海地质.北京:科学出版社,2001 Liu Z S, Zhao H T ,Fan S Q, The continental margin spreading of South China Sea and the cycle of evolution of marginal seas. In:Journal of Tropical Oceanography ( in Chinese). Beijing: Science Press, 2001
[7] 张云帆,孙珍,周蒂等.南海北部陆缘新生代地壳减薄特征及其动力学意义.中国科学,2007,37(12) :1609-1616 Zhang Y F, Sun Z, Zhou D, et al. The Cenozoic crust thinning characteristics and its dynamics meaning of northern margin of South China Sea. Science in China (in Chinese).2007,37(12) :1609-1616
[8] 周蒂,刘海龄.南沙海区及其周缘中一新生代岩浆活动及构造意义.大地构造与成矿学,2005,29(3) :354-363 Zhou D, Liu H L. Mesozoic-Cenozoic magmatism in southern South China Sea and its surrounding areas and its implications to tectonics. Geotectonica et Metallogenia (in Chinese). 2005,29(3) :354-363
[9] 周蒂,陈汉宗.南海的右行陆缘裂解成因.地质学报,2002,76(2) :180-190 Zhou D,Chen H Z, Opening of the South China Sea by dextral splitting of the East Asian Continental margin. Acta Geologica Sinica (in Chinese), 2002,76(2) :180-190
[10] 何廉声.南海地质构造图.见:南海地质地球物理图集.广州:广东科技出版社,1987 He L S. Geological structure map of South China Sea. In:Geology and Geophysics Atlas of South China Sea (in Chinese). Guangzhou: Guangdong Science and Technology Press, 1987
[11] Tian Z, Han P, Xu K. The Mesozoic-Cenozoic East China rift system. Tectonophysics, 1992,208(1-3) :341-363
[12] 袁玉松.南海北部陆缘深水区构造-热演化与烃源岩成熟度史研究[博士学位论文].北京:中国科学院地质与地球物理研究所,2007 Yuan Y S. Tectonothermal evolution and source rock maturation history in deep water area of the northern margin of the South China Sea [Ph. D. thesis](in Chinese). Beijing: Institute of Geology and Geophysics, Chinese Academy of Sciences, 2007
[13] 张功成,米立军,吴时国等.深水区-南海北部大陆边缘盆地油气勘探新领域.石油学报,2007,28(2) :15-21 Zhang G C, Mi L J, Wu S G, et al. Deepwater area-the new prospecting targets of northern continental margin of South China Sea. Acta Petrolei Sinica (in Chinese), 2007,28 (2) :15-21
[14] Karig D E. Origin and development of marginal basins in the western Pacific. J. Geophys. Res. ,1971,76:2543-2561
[15] Tapponnier P, Molnar P. Slip-line field theory and large scale continental tectonics. Nature, 1976,264:319-324
[16] 阎贫,刘海龄.南海北部陆缘地壳结构探测结果分析.热 带海洋学报,2002,21(2) :1-12 Yan P, Liu H L. Analysis on deep crust sounding resulting northern margin of South China Sea. Tropic Oceanology (in Chinese), 2002,21(2) : 1-12
[17] 姚伯初,万玲,吴能友.南海新生代构造演化及岩石圈三维结构特征.地质通报,2005,24(1) :1-8 Yao B C. Wan L, Wu N Y. Cenozoic tectonic evolution and the 3D structure of the lithosphere of the South China Sea. Regional Geology of China (in Chinese), 2005,24(1) :1-8
[18] 王家林,张新兵,吴健生等.珠江口盆地基底结构的综合地球物理研究.热带海洋学报,2002,21(2) :14-22 Wang J L, Zhang X B, Wu J S et al. Integrated geophysical researches on base texture of Zhujiang River Mouth Basin. Tropic Oceanology (in Chinese), 2002 ,21(2) :14-22
[19] Nissen S, Hayes D, Buhl P, et al. Deep penetration seismic sounding across the north margin of South China Sea. J. Geophys. Res., 1995,100(Bl1) :22407-22433
[20] Nissen S, Hayes D, Yao B, et al. Gravity, heat flow, and seismic constraints on the processes of crustal extension: Northern margin of South China Sea. J. Geophys. Res. , 1995,100(1111) :22447-22483
[21] 滕吉文,王谦身,魏斯禹.中国地壳构造的基本轮廓.石油物探,1982,2:14-30 Teng J W, Wang Q S, Wei S Y. The basic contour map of China crustal structure. Geophysical Prospecting for Petroleum (in Chinese), 1982,2:14-30
[22] Christensen N I, Mooney W D. Seismic velocity structure and composition of the continental crust; a global view. J. Geophys. Res. ,1995,100:9761-9788
[23] Zhang Z J, Zhang X, Badal J. Composition of the crust beneath Southeastern China derived from an integrated geophysical dataset. Journal of Geophysical Research , 2008 , 113(B4) , B04417, doi:10． 1029/2006JB004503
[24] Zhang Z J, Badal J, Li Y, et al. Crust-upper mantle seismic velocity structure across Southeastern China. Tectonophysics , 2005, 395:137-157
[25] Zhang Z J. Wang Y H. Crustal structure and contact relationship revealed from deep seismic sounding data in South China. Physics of the Earth and Planetary Interiors , 2007,165:114-126
[26] 袁学诚,左愚,蔡学林等.华南板块岩石圈构造与地球物理.见:80年代中国地球物理学进展.北京:学术书刊出版社.1989． 243-249 Yuan X C, Zuo Y, Cai X L, et al. The structure of the lithosphere and the geophysics in the South China plate geophysics in China. In Commemoration of the 80th Birthday of Professor Fu Chengyi (in Chinese). Beijing: Academic Journal Press, 1989． 243-249
[27] 廖其林,王振明,朱介寿.福州-泉州-汕头地区地壳结构的爆炸地震研究.地球物理学报,1986,3:270-280 Liao Q L, Wang Z M, Zhu J S. Explosion seismic study of the crustal structure in Fuzhou-Quanzhou-Shantou region. Chinese J.Geophys. (in Chinese), 1986,3:270-280
[28] Fan W, Amenzies M. The lithospheric mantle composition of volcanism in extension settings: the geochemical evidence of Cenozoic basalts in Leiqiung area. lit; Liu R Ed. The Ages and Geochemistry of Cenozoic Volcanic Rocks in China. Beijing:Seismological Press,1992． 320-329
[29] Zhu B, Wang H. Nd-Sr-Pb isotope and chemical evidence for the volcanism with MORB-OIB source characteristics in the Leiqiong area, China. Geochimica, 1989,18(3) :193-201
[30] Xia B, Zhang Y, Cui X J, et al. Understanding of the geological and geodynamie controls on the formation of the South China Sea:A numerical modelling approach. Journal of Geodynamics,2006,42:63-84．
[31] Zhang Z J, Bai Z M, Mooney W D, et al. Crustal structure across the Three Georges areas of the Yangtze platform, central China, from seismic refraction/wide-angle reflection data. Tectonophysics, 2009,475:423-437, doi:10． 1016/j. tecto. 2009． 05． 022
[32] Thybo H, Maguire P K H, Birt C.et al. Seismic reflectivity and magmatic underplating beneath the Kenga Rift. Geophys. Res. Lett. , 2000,27( 17) :2745-2748
[33] Thybo H, Nielsen C A. Magma-compensated crustal thinning in continental rift zones. Nature,2009,457:873-876
[34] 张中杰,刘一峰,张素芳等.东南盆地地壳伸展特征及其动力学意义.地球物理学报,2009(待发表) Zhang Z J, Liu Y F. Zhang S F, et al. Crustal extension fatures in Qiongdannan basin and its tectonic implications. Submitted to Chinese J. Geophys. (in Chinese), 2009
[35] Wang Y J, Fan W M, Guo F, et al. Geochemistry of Mesozoic mafic rocks adjacent to the chenzhou-cinwufault, South China. Implication for the lithospheric boundary between the Yangtze and Cathaysia blocks. Int. Geol. Rev. ,2003,45:263-286
[36] Li Z X, Li X H. Formation of the 1300 km wide intracontinental-orogen and postorogenic magmatic province in Mesozoic South China; A flat-slab subduction model. Geology, 2007 ,35:179-182
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